Communications network with routing tables for establishing a path without failure by avoiding unreachable nodes

A cross-connect node for a communications network in which said node comprises one of a plurality of network nodes, said network nodes being organized into a plurality of groups corresponding to geographic domains, ones of said network nodes located at a periphery of the network functioning as edge nodes to which user terminals are connected, said cross-connect node comprising:

• a domain connectivity table for indicating an unavailability of an intra-domain connectivity of the domain of said cross-connect node;
• a domain routing table for indicating a route specifying ones of said network nodes whose intra-domain connectivity is indicated in said domain connectivity table, the domain routing table including a plurality of parallel routes between said source and destination terminals, each of said plurality of parallel routes repeatedly passing through the domain of the cross-connect node;
• and
• a processor for using said domain routing table for establishing a path between said edge nodes in response to a path setup request from said user terminals by selecting one of said parallel routes having a smallest number of transit domains and discarding the parallel routes other than the selected route from the routing table.

An operating method for a communications network, wherein the network comprises a plurality of network nodes being organized into a plurality of groups corresponding to geographic domains, ones of said network nodes located at a periphery of the network functioning as edge nodes and a plurality of user terminals connected to said edge nodes, the method comprising:

• creating a domain connectivity table for indicating an unavailability of an intra-domain connectivity of an associated one of said plurality of domains;
• creating a domain routing table for indicating a route specifying ones of said network nodes whose intra-domain connectivity is indicated in said domain connectivity table, the domain routing table including a plurality of parallel routes between said source and destination terminals, each of said plurality of parallel routes repeatedly passing through the domain of the cross-connect node;
• advertising contents of the domain routing table to the network nodes of a downstream neighbor domain;
• updating the domain routing table in accordance with advertised contents of the routing table of an upstream neighbor domain;
• and
• using said domain routing table for establishing a path between said edge nodes in response to a path setup request from said user terminals by selecting one of said parallel routes having a smallest number of transit domains and discarding the parallel routes other than the selected route from the domain routing table.

A communications network comprising:

• a plurality of network nodes organized into a plurality of groups corresponding to geographic domains, ones of said network nodes located at a periphery of the network functioning as edge nodes to which user terminals are connected, and ones of said network nodes located at border points between neighbor domains of said plurality of domains functioning as border nodes, the border nodes of same domain being interconnected by intra-domain virtual links and the border nodes of different domains being interconnected by inter-domain physical links;
• a plurality of domain routing tables respectively associated with said domains, each of the domain routing tables indicating a plurality of routes containing no intra-domain virtual link terminating at said edge nodes and no consecutively concatenated intra-domain virtual links, each of the domain routing tables including a plurality of parallel routes between said source and destination terminals, each of said plurality of parallel routes repeatedly passing through the associated domain;
• and
• a backbone routing table for indicating a plurality of inter-domain routes and unreachability indications between the border nodes of each domain and the border nodes of every other domain, said inter-domain routes containing at least one of said inter-domain physical links but containing no consecutively concatenated intra-domain virtual links,
• said network nodes using said domain routing tables and said backbone routing table for establishing a path between said edge nodes in response to a path setup request from said user terminals by selecting one of said parallel routes having a smallest number of transit domains and discarding the parallel routes other than the selected route from the domain routing table.

A cross-connect node for a communications network in which said node comprises one of a plurality of network nodes, said network nodes being organized into a plurality of groups corresponding to geographic domains, ones of said network nodes located at a periphery of the network functioning as edge nodes to which user terminals are connected, and ones of said network nodes located at border points between neighbor domains of said plurality of domains functioning as border nodes, the border nodes of a same domain being interconnected by intra-domain virtual links and the border nodes of different domains being interconnected by inter-domain physical links;

• a domain routing table for indicating a plurality of routes containing no intra-domain virtual link terminating at said edge nodes and no consecutively concatenated intra-domain virtual links, the domain routing table including a plurality of parallel routes between said source and destination terminals, each of said plurality of parallel routes repeatedly passing through the associated domain;
• a backbone routing table for indicating a plurality of inter-domain routes and unreachability indications between the border nodes of each domain and the border nodes of every other domain, said inter-domain routes containing at least one of the inter-domain physical links but containing no consecutively concatenated intra-domain virtual links;
• and
• a processor for using said domain routing table and said backbone muting table for establishing a path between said edge nodes in response to a path setup request from said user terminals by selecting one of said parallel routes having a smallest number of transit domains and discarding the parallel routes other than the selected route from the domain routing table.

An operating method for a communications network which comprises a plurality of network nodes organized into a plurality of groups corresponding to geographic domains, ones of said network nodes located at a periphery of the network functioning as edge nodes to which user terminals are connected, and ones of said network nodes located at border points between neighbor domains of said plurality of domains functioning as border nodes, the border nodes of a same domain being interconnected by intra-domain virtual links and the border nodes of different domains being interconnected by inter-domain physical links, the method comprising:

• creating a plurality of domain routing tables respectively associated with said domains, each of the domain routing tables indicating a plurality of routes containing no intra-domain virtual link terminating at said edge nodes and no consecutively concatenated intra-domain virtual links, each of said domain routing tables including a plurality of parallel routes between said source and destination terminals, each of said plurality of parallel routes repeatedly passing through the associated domain;
• creating a backbone routing table for indicating a plurality of inter-domain routes and unreachability indications between the border nodes of each domain and the border nodes of every other domain, said inter-domain routes containing at least one inter-domain physical link but containing no consecutively concatenated intra-domain virtual links;
• and
• using said domain routing tables and said backbone routing table for establishing a path between said edge nodes in response to a path setup request from said user terminals by selecting one of said parallel routes having a smallest number of transit domains, and discarding the parallel routes other than the selected route from the domain routing table.